By SupplementenscannerHow we compare
Ferrous sulfate on the front, elemental iron further down
An iron pack names a compound on the front, ferrous sulfate, ferrous fumarate, ferrous gluconate or iron bisglycinate, with milligrams beside it. Those milligrams weigh the whole compound. The elemental iron is a separate line below, printed as "of which iron", and the NRV percentage next to it is worked out on that second figure. Only the second figure puts two packs on the same footing. The same arithmetic is set out for another mineral in buying magnesium.
The ranking then orders on price per tablet or per capsule, and goes no further. One dose is never converted into another, the filters that appear cover diet and quality marks such as vegan or gluten free rather than form or dose, and a product stocked by two shops holds two separate rows, each at its own price.
Tonics, sachets and the word "gentle"
"Gentle iron" is printed on British packs as a selling line, not as a specification, and a ranking cannot read it. The compound is in the ingredient list and the milligrams are in the panel, and two packs both calling themselves gentle can differ on both.
Tonics and sachets are the other British format, sold by the bottle or by the box. A bottle earns a price per dose only when its label states how many doses or how many millilitres make one, so a tonic and a tablet meet only after that division has been done.
Two searches that are names rather than categories
Two of the searches gathered here have no category behind them, and both are compared at the pack price. "Iron bisglycinate" returns brands and own-brand ranges: the word settles the compound and leaves the milligrams to the panel, where they change from one brand to the next.
"Lactoferrin" returns something that is not iron at all. It is a milk protein, its packs count milligrams of lactoferrin per capsule, and the allergen line names milk. No iron figure appears, because none is dosed. Packs under either of the two names differ in count, so the price per capsule is a division you make rather than one you read.
Vitamin C, B12 and a multivitamin with iron: one label, two scales
Plenty of iron packs sell vitamin C in the same tablet. What that pairing costs above a plain iron tablet shows up when you set plain vitamin C next to it: that one is ranked per capsule and sells as ascorbic acid, as buffered calcium ascorbate and as Ester-C, in doses that differ sharply from pack to pack.
On B12 and folic acid the unit shifts: B12 is dosed in micrograms and iron in milligrams, so a combined tablet prints two scales one under the other. A multivitamin with iron gives iron a single line in a long table and is ranked per tablet against other multivitamins rather than against iron tablets.
Searches that add women, anaemia or the letters UK land on these same packs with a different heading above them, and adding a chemist's name to a search picks a seller rather than a formula. Beyond that there is reading a supplement label, and iron returns on energy and focus, pregnancy and breastfeeding, each with the ingredients searched for beside it there.